The present invention relates to an apparatus and a method for detecting abnormal balls such as connected balls, etc. among a large number of small balls, most of which are separate balls.
Small balls made of metals, resins or glass, etc. and required to have high sphericity are produced from melts by various methods. For instance, small metal balls such as solder balls are produced by ejecting and cooling a molten metal in a gas or a solvent. This production method, however, forms abnormal balls, such as connected balls constituted by a plurality of balls, balls having sizes outside the permitted range, balls having sphericity outside the permitted range, for instance, ellipsoids, etc., in addition to good separate balls within the predetermined ranges of size and sphericity. Though most of balls outside the permitted size range can be removed by a sieve, for instance, connected balls, which may have the same diameters as those of separate balls depending on their directions, pass through sieve openings, it is impossible to completely remove all the connected balls from a large number of separate balls. Accordingly, the connected balls should be detected among a large number of balls and removed therefrom.
Conventionally used to detect connected balls among a large number of small balls is a so-called slope rolling method as described in, for instance, Japanese Patent Laid-Open No. 11-319728. This method utilizes the fact that good separate balls and connected balls fall differently when rolling down on a slope. This method is advantageous in that it can be conducted by an apparatus having a simple structure. However, this method is disadvantageous in that connected different-diameter balls cannot necessarily be detected with high precision, though connected balls having the same diameter can be detected with high precision.
Proposed by Japanese Patent Laid-Open No. 11-319722 to detect good separate balls and connected different-diameter balls with high precision is an apparatus comprising a member having a slanting surface on which a large number of small balls roll down, a means for supplying a large number of small balls to the slanting surface, a means for collecting good separate balls rolling down the slanting surface, and grooves in parallel with the rolling direction of the balls between the supply means and the slanting surface and/or on the slanting surface. Though the good separate balls continue rolling down even when entering into the grooves, the connected different-diameter balls entering into the grooves do not roll down, because their center axes are in alignment with the rolling direction, whereby small-diameter balls act as wedges between the grooves and large-diameter balls.
In the above apparatus comprising slanting grooves, however, the slanting angle, shape, size, etc. of the grooves affecting the detecting precision of connected balls should be detected depend on balls to be detected. This apparatus thus fails to detect abnormal balls efficiently. In addition, the produced balls contain not only connected identical-diameter balls constituted by a plurality of balls having substantially the same size, but also connected different-diameter balls having extremely small balls connected. Though connected identical-diameter balls fall with their center axes without alignment with the rolling direction, a wedge action does not work even though their center axes are in alignment with the rolling direction. Also, the connected different-diameter balls include those behaving similarly to good separate balls, in which only large-diameter balls roll down. Further, there are connected balls that fall along the slanting grooves without stopping. Accordingly, it is difficult to detect the connected balls among a large number of small balls with high precision by the above apparatus.
Accordingly, an object of the present invention is to provide an apparatus and a method for detecting abnormal balls such as connected balls, etc. among a large number of small balls with high precision.
The apparatus for detecting abnormal balls among a large number of balls, most of which are good separate balls, according to one embodiment of the present invention comprises a ball-holding means having a large number of ball-receiving cavities each receiving one ball, and a means for detecting part of a ball projecting from each ball-receiving cavity, the determination of the abnormal balls being carried out by utilizing the detection information of projecting portions of the balls.
The apparatus for detecting abnormal balls among a large number of balls, most of which are good separate balls, according to another embodiment of the present invention comprises a ball-holding means having a large number of ball-receiving cavities each receiving one ball, a means for detecting part of a ball projecting from each ball-receiving cavity, and a means for carrying out the determination of abnormal balls based on the detection information of projecting portions of the balls.
The abnormal ball-detecting apparatus of the present invention further comprises a means for separating balls determined as abnormal balls from good separate balls.
The ball-receiving cavity preferably has a depth substantially equal to and a diameter slightly larger than the diameter of each good separate ball.
The ball-receiving cavities may be formed directly in the support member, or may be formed by a combination of a member having through-holes and a support member having a flat surface. Good separate balls are preferably supported by the bottom of the ball-receiving cavities, with their top points in the same plane as the upper edges of the ball-receiving cavities.
The ball-holding means is preferably formed by attaching an apertured sheet member to an outer surface of a cylindrical support member. Specifically, the ball-holding means comprises an apertured sheet member having a thickness substantially equal to the diameter of each separate good ball and through-holes each having as large a diameter as 1 to 1.2 times the diameter of each separate good ball, and a support member having a flat surface attached to the apertured sheet member, the ball-receiving cavities being formed by the through-holes of the apertured sheet member and the support member. Here, xe2x80x9csubstantially the same as the diameter of a separate ballxe2x80x9d means that a ball has a diameter in a range of the nominal diameter of a separate ball plus such permitted error ranges as the dimensional tolerance of a separate ball, the formation error of a ball-receiving cavity, etc.
According to one embodiment of the present invention, the projecting ball-detecting means comprises a light source for emitting a light beam toward the ball-receiving cavities, and a light receptor for receiving a light beam passing over the surface of each ball-receiving cavity, and when part of a ball is projecting from a ball-receiving cavity, the light beam is intercepted thereby detecting that the ball is projecting from the surface of the ball-receiving cavity.
According to another embodiment of the present invention, the projecting ball-detecting means comprises a light source for emitting a light beam toward the ball-receiving cavities, and a light receptor for receiving a light beam reflected from part of a ball projecting from a ball-receiving cavity, thereby detecting that the ball is projecting from the surface of the ball-receiving cavity.
The method for detecting abnormal balls among a large number of balls, most of which are good separate balls, according to one embodiment of the present invention comprises introducing balls into cavities each having a predetermined depth, optically detecting part of a ball projecting from each cavity, and carrying out the determination of abnormal balls by a determination logic utilizing detection information of the balls.
The method for detecting abnormal balls among a large number of balls, most of which are good separate balls, according to another embodiment of the present invention comprises introducing balls into cavities each having substantially the same depth as the diameter of each separate good ball; optically detecting part of a ball projecting from the cavity; and determining balls projecting more than a reference level as abnormal balls.
The apparatus for detecting and removing abnormal balls among a large number of balls, most of which are separate good balls, according to a further embodiment of the present invention comprises (a) a rotatable, cylindrical, ball-holding means comprising a large number of ball-receiving cavities each receiving one ball; (b) a means for detecting part of a ball projecting from each ball-receiving cavity in a detection region substantially at a top of the cylindrical ball-holding means; (c) a ball-supplying means disposed upstream of the detection region on the cylindrical ball-holding means; (d) an abnormal ball-removing means disposed on the cylindrical ball-holding means downstream of the detection region; (e) a means for collecting good separate balls disposed downstream of the detection region; and (f) a means for carrying out the determination of abnormal balls based on the detection information of projecting portions of the balls obtained by the projecting ball-detecting means.
The apparatus for detecting and removing abnormal balls among a large number of balls, most of which are good separate balls, according to a further embodiment of the present invention comprises (a) a rotatable, cylindrical, ball-holding means comprising a large number of ball-receiving cavities each receiving one ball, the air being movable through the ball-receiving cavities between the inside and outside of the cylindrical ball-holding means; (b) a stationary member having three rib portions disposed inside the cylindrical ball-holding means, each rib portion being in contact with the inner surface of the cylindrical ball-holding means in a substantially air-tight manner, a reduced-pressure region defined by a first rib portion, a second rib portion and the inner surface of the cylindrical ball-holding means being disposed in an upper portion of the cylindrical ball-holding means, an atmospheric-pressure region defined by a second rib portion, a third rib portion and the inner surface of the cylindrical ball-holding means being disposed downstream of the reduced-pressure region, and a high-pressure region defined by a third rib portion, a first rib portion and the inner surface of the cylindrical ball-holding means being disposed in a lower part of the cylindrical ball-holding means downstream of the atmospheric pressure region; (c) a means for detecting part of a ball projecting from each ball-receiving cavity substantially at a top of the cylindrical ball-holding means in a detection region disposed in the reduced-pressure region; (d) a ball-supplying means disposed on the cylindrical ball-holding means upstream of the detection region in the reduced-pressure region; (e) an abnormal ball-removing means disposed on the cylindrical ball-holding means downstream of the detection region in the atmospheric pressure region; (f) a means for collecting good separate balls disposed downstream of the detection region in the high-pressure region; and (g) a means for carrying out the determination of abnormal balls based on the detection information of projecting portions of the balls obtained by the projecting ball-detecting means.
The apparatus for detecting and removing abnormal balls among a large number of balls, most of which are good separate balls, according to a further embodiment of the present invention comprises (a) a rotatable, ball-holding belt means comprising a large number of ball-receiving cavities each constituted by a through-hole for receiving one ball; (b) a pair of pulleys for rotatably supporting the ball-holding belt means; (c) a flat plate disposed immediately under a horizontal portion of an upper half of the ball-holding belt means, a surface of the ball-holding belt means being slidable over the flat plate; (d) a means for detecting part of a ball projecting from each ball-receiving cavity in a detection region on the flat plate; (e) a ball-supplying means disposed on the ball-holding belt means upstream of the detection region on the flat plate; (f) an abnormal ball-removing means disposed on the ball-holding belt means downstream of the detection region on the flat plate; (g) a means for collecting good separate balls disposed at a rear end of the flat plate; and (h) a means for carrying out the determination of abnormal balls based on the detection information of projecting portions of the balls obtained by the projecting ball-detecting means.
The apparatus for detecting and removing abnormal balls among a large number of balls, most of which are good separate balls, according to a further embodiment of the present invention comprises (a) a rotatable, ball-holding belt means comprising a large number of ball-receiving cavities each receiving one ball; (b) a pair of different-diameter pulleys for rotatably supporting the ball-holding belt means, a center of a larger-diameter pulley being positioned higher than a center of a smaller-diameter pulley; (c) a means for detecting part of a ball projecting from each ball-receiving cavity in a detection region substantially at a top of the larger-diameter pulley; (d) a ball-supplying means disposed a upstream of the detection region on the ball-holding belt means on the larger-diameter pulley; (e) an abnormal ball-removing means disposed downstream of the detection region on the ball-holding belt means on the larger-diameter pulley; (f) a means for collecting good separate balls disposed downstream of the detection region; and (g) a means for carrying out the determination of abnormal balls based on the detection information of projecting portions of the balls obtained by the projecting ball-detecting means.